If your hunch that the antibiotics' effects on your gut bacteria was the cause is correct, have you considered a fecal microbiota transplant to restore a healthier mix?
Yes! In 2019, the experimental medicine department at my local university hospital started scheduling FMT procedures. They're suspended now because of COVID-19 restrictions (much like dentists and optometrists). But I'm in the queue. Somewhat awkwardly, I am responsible to nominate a suitable donor.
I don't know where you are, but with so many medical workers now vaxxed in US, my impression is hospitals/etc are mostly eager to catch up on delayed non-pandemic procedures.
If your own nearest option is still slow or requires a personally-nominated donor, other providers offering the freeze-dried pills, perhaps even via telemedicine, might be an option. Good luck!
For what it's worth, I asked this question sincerely. There are people who do it themselves, and I was curious about the tradeoff he saw between risk / reward of doing it this when there was a long wait.
https://en.wikipedia.org/wiki/Fecal_microbiota_transplant